There are times in life when you discover that the strongest player on your team, or your best talent, or your sharpest debating point, has absolutely no chance of prevailing against your opponent. No matter what you do or how hard you try, your team is nowhere near good enough to win. According to the writer of the Letter to the Hebrews in chapter 5, that’s how it was with the old system of animal sacrifices, because you had to be perfect and sinless to be on good terms with God, and even the high priest was a fallible sinful person.
Every high priest selected from amongst humans is appointed to represent people in their dealings with God, to offer gifts and sacrifices for sins. The high priest can empathise with people who are ignorant and misguided, because he himself suffers weaknesses. Because of this, he must offer sacrifices for sins for himself, as well as for the people.
Any sins which anyone committed had to be dealt with in order to win back God’s favour. This involved offering animal sacrifices, with the death of the animal being a substitute for the death that the sinner deserved as a consequence of committing the sin. The system of sacrifices was like a dog chasing its tail. No sooner had a sacrifice been made than more sins had been committed, even by the guy who was making the sacrifices. The only solution was to have a perfect, once-for-all sacrifice to take away sins forever.